At 36, Mark Webber concedes age and impending rule changes in Formula One were major factors in his decision to quit the sport.

But the veteran of 203 Grands Prix made up his mind a long time ago and says he is now one happy boy.

The Australian Red Bull driver will switch to sportscar racing with Porsche’s LMP1 team from 2014, in a category that nearly cost him his life 15 years ago.

Webber dismissed claims his strained relationship with teammate Sebastian Vettel had pushed him out the door, saying several factors persuaded him to leave – including his age.

“There’s lot of reasons that come into the pot,” he said on the eve of opening practice for this weekend’s British Grand Prix.

“There’s going to be big, big changes in the sport next year.

“So let’s see how the category is next year in Formula One. I’ll be interested to watch every now and then and watch these guys do their stuff.”

Webber made the announcement on Thursday via a statement from Porsche posted on his personal website, to which he tweeted a link saying: “Happy boy!”.

He denied the move was in any way a dig at Red Bull, simply adding that “it was about Porsche and Mark Webber today”.

“The timing is perfect for me,” he said.

“I’ve known for quite a while, and had a plan and stuck to it.

“But still I will be focusing on achieving very, very strong results in my last season in Formula One.”

He said he had been in touch with Red Bull owner Dietrich Mateschitz over his future for a number of months and was well-supported.

“He certainly encouraged me not to rush my decision when I approached him earlier in the season.”

Also supportive of Webber’s decision was Australian Grand Prix boss Ron Walker.

“Mark ranks alongside Alan Jones MBE and Sir Jack Brabham AO OBE as true legends of Formula One,” Walker said in a statement.

“His contribution to the popularity of the sport in his home country cannot be underestimated, and we wish him all the best in the next phase of his career.”

Webber, who has won nine grands prix in his 12-year career, says he intends to compete as hard as ever in the final 12 races of his F1 career.

The first of those is on Sunday at Silverstone, where he has won two of the past three races.